The TT website says they're only available for pre-order, so you might struggle to find anyone who's tried them yet! I'm also struggling to see what you'd have to drop the bike on for these to do any good, and I say that as an expert in dropping motorcycles
After losing some ground due to introducing water cooler, BMW engineers struggle to find ways to save weight. Often the weight saving efforts are dismissed in Tosserland as 'Wanker bean counting accountants, feckin with things'..... Only for Tossers to stack more weight on their awesome steed.